Perfboard for Mac

From Pepsan & Associates, Inc.:

Perfboard provides an extensive readout of system performance data for Mac OS X. Areas monitored include CPU load metrics, memory statistics, network bandwidth, and disk I/O operations. Feel your system has bogged down? Run Perfboard and check at a glance for problems such as excessive virtual memory paging, high network activity, lack of free memory, runaway processes and more.
The Perfboard download package includes a Readme file giving a brief overview of the program plus a Manual that describes the application, provides information on each of the metrics reported by Perfboard and gives tips on what to look for if using Perfboard to troubleshoot a system slowdown.
Perfboard initially opens with a meter displaying the CPU busy percentage in the top left quadrant, a graph of total network traffic in the top right quadrant, and text display of all the metrics in the bottom half of the window. In the snapshot below, the graph has been switched to show the current number of free memory pages. Perfboard is free but donations are accepted via the web page or file included in the distrubution.